1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more specifically, to a method of forming a source contact of a flash memory device.
2. Discussion of Related Art
Generally, in manufacturing a semiconductor device, a polysilicon film or a tungsten film is used to form a source contact of a flash memory device.
If the polysilicon film is used in the source contact, burial characteristics are good. If a thermal treatment process is used, however, there are problems in that a process time lengthens, and a metal line and contact resistance become high.
Meanwhile, if the tungsten film is used in the source contact, the metal line and contact resistance are better than those when the polysilicon film is used. However, the tungsten film is easily oxidized at a temperature of about 400° C., a silicide film is formed at a temperature of about 600° C., and adhesive force is poor in an oxide film or a nitride film. This requires a deposition process of a junction layer to be added.
In the case where a titanium film is used as the junction layer, there is a problem in that a process of forming metallic anti-diffusion films has to be added in order to prevent a combination of the titanium film having high reactivity with a reaction gas of tungsten.